Conventional configurable circuits include Field Programmable Gate Array (FPGA) circuits marketed by the company Xilinx. These circuits are made up of look-up tables or memories that can be programmed independently, and interconnection elements that are also programmable. The look-up tables have a fine programming granularity, generally to the bit level, and can be used to implement conventional logic functions such as OR and AND functions, for example, with two or three inputs.
When implementing a multiplier with such circuits, the result is a circuit having a large surface area. Families of products marketed by Xilinx, such as the products of the Virtex family, do indeed incorporate multipliers, for example, 18×18 bit multipliers. However, the designer is faced with some inflexibility in programming these multipliers, since it is difficult to produce, from these 18×18 bit multipliers, 8×8 bit multipliers or 32×32 bit multipliers, for example.